A Demon's Promise
by Sneebs
Summary: When the Pine twins go out on an adventure, Dipper gets very badly hurt, and Mabel feels responsible. As she's kneeling over her unconscious brother's body, a certain dream demon appears, and tries to strike a deal.
1. Chapter 1

"Mabel! Hand me the butterfly net, and _hurry!"_

The twelve-year-old girl looked around her frantically, but the net was nowhere to be seen.

"Mabel!"

She got down on her hands and knees, and began rooting around in the underbrush. She found something, gripped it tight, and raised it from the ground, brushing dry, crinkled leaves off of it. Without a second's thought she lept up and handed it to her brother, who groaned.

"Mabel, this is a _tree branch!_"

Perhaps she should've looked at the item before handing it to Dipper.

"It would be really nice if I _had that net right now!" _her brother hollered, panicked. There was something else in his voice, too...he sounded...scared?

She got down on the ground once again._ Why can't I find it? _she wondered. Then, an idea struck her suddenly, like a van full of 'd looked everywhere in the underbrush, on the trail, and inside the withered trees' trunks, but she'd never once thought to look _up._

"MABEL!" called Dipper again. After he yelled to her, there were multiple whistling sounds, like something zipping through the air.

She saw it, hanging there in the tree above. Scuffling toward the trunk, she grabbed onto it and began to shimmy up the crusty surface. She was so close to the butterfly net, it was nearly in her hands-

The bark underneath one of her hands detached from the tree trunk, and Mabel lost her balance. She fell back down the tree about two feet before catching herself on one of the branches.

"_MABEL!" _The zipping noises were all around, and they were overwhelming. Mabel wanted to look to quench her curiosity, and to see what they were. But she knew she had to get that net.

She pushed herself up. Her hand just barely touched it...and…

She grabbed the handle, and with a small sound of victory, she scuttled back down the red tree. She turned around, waving the net and running to Dipper, enthusiastically saying, "I got the butterfly net, Dipper! I got it! Dip-"

She stopped dead in her tracks. The net slid from her suddenly sweaty palm and bounced off of the mossy rock on which she stood with a metallic ring. She didn't pick it up, though. Her eyes were glued on the lump of blue, orange, and brown that lay on the floor in front of her. Time froze as Mabel realized everything had gone completely silent - the squirrels, scurrying busily through the trees, the woodpeckers peck peck _pecking _at wood, in search of bugs to eat, the gentle breeze of a cool summer day sighing as it glides through the forest on soft feet.

Underneath that crumpled mess of orange, blue, and brown, was her brother. He looked too small for his clothes, as he lay there on the green and yellow moss. His breathing was shallow, and every time the boy's lungs released a breath, there was a longer pause before the next inhale.

Mabel fell to her knees beside Dipper, pushing away the dead, torn leaves that were still on the ground from last fall. She rolled him over onto his back, and set his head on top of a nearby soft, collapsing section of rotted wood that had come from a tree that had fallen long ago. Her brother's eyes peered up, up toward the canopy, then rolled around from inside of a scratched, pale face, and only stopped when they found her.

"Mabel…" he said, his voice just a breath. It sounded like part of the breeze. If Mabel hadn't seen her brother's lips move, she would have thought the trees were singing to her in hushed tones.

"Dipper," she said, her voice small. "Dipper, look at me, bro! I'm gonna go get help. We're gonna get through this-" She began to stand, but Dipper grabbed her wrist. His grasp was disturbingly weak. Mabel, though she could've easily swatted it away, and run off to find someone who could fix this, fix Dipper...she stayed, bringing up her other hand and cusping it over the top of the hand that held her wrist.

"No, Mabel...there's nobody close around, I studied the map before coming, the area's...practically deserted…"

She wasn't sure what to do. Simply sitting beside her brother, watching the life slowly drain from him, paling and graying his skin, and making his eyes nothing but blank mirrors that stared back up at her with a serene calm - she couldn't just sit there, and watch it all happen.

Dipper was dying.

She hadn't gotten him the net in time.

It was _her fault. _

"Wha-what if there's a tourist or something. I mean, this is Gravity Falls! There's always tourists!"

Dipper focused his last ounce of strength toward holding on to her. "Don't leave me," he breathed.

Mabel sat back down. She could do something….there had to be someone around…._anyone._

Dipper's eyes fluttered shut, but his hand still held onto her, like it was his only tie, his lifeline. He was drifting from the shore, away from the edge of the dock, the waves carrying him into the fog that hung over the water. She was a frail rope, stretching, reaching, and holding onto him.

She had to go get help, to find a way to save Dipper! But she couldn't leave him - he didn't want her to go away. They were born together, side-by-side, and they'd grown up throughout the years, always the perfect fitting piece to each other's puzzles and troubles. They'd sung and danced synchronized jigs, helped each other through the loss of household pets and close friends, and had always been there to complete each other's sentences. And - _oh boy! _- the adventures they'd shared in Gravity Falls. A place of mystery and danger, a place so thrilling it pulls young minds run on curiosity in and it...it…

They'd always been there for each other, and just as they were born at each others' side, Dipper wanted to die by Mabel.

Mabel wasn't sure how long it had been, watching her brother lay on the cold stone and rotted log, his breath slowing in a gentle ritardando, gradually easing into nothing but a slight wheezing.

She lay her head on his chest so she could listen to his last inhales and exhales, his last threads of life. He opened his eyes the slightest of a bit, just to look at her, and she could have sworn she saw the very corner of his mouth twitch upward, as though to say, _Hey Mabel, it's okay. It'll be just like when I went to summer camp a year ago - you might miss me at first but you'll soon ease into a new rhythm._

What was she going to do without her twin? He was the other side to her puzzle, the one who always had the answer when she didn't! Dipper was the one upon whom she could depend, could entrust with her deepest, darkest secrets.

Dipper's grip on her wrist slackened. He'd held on until the very end, until he simply couldn't anymore.

"No, no, no!" she cried, her voice rising in pitch. "Dipper, wake up. Wake up, Dipper!" She looked at him through eyes full of tears. "Why won't you wake up?" Mabel whined.

She still held his palm in both of hers. It was so cold. Why was it so cold?

"Help!" she yelled, her voice cracking. "Help! He's-he's dying!" She placed her forehead on his chest and sobbed silently, the wails having nowhere to go but inside, all tight and stiff, where they wracked through her whole body. She shook uncontrollably.

"_It's a little late for that, Shooting Star," _came a voice that shook the trees. _"The kid's already dead."_

Mabel jolted upright, sniveling and wiping at tears in her eyes. She scowled, recognizing the voice and the wretched demon it belonged to. "BILL," she screamed. "You did this, didn't you? It's _your fault!" _She grabbed the nearest rocks that lay next to her and Dipper and began throwing them with all the strength that she could muster, but no matter how many she threw, or where she threw them, the entity easily dodged every single one. He even dodged the butterfly net when she chose to throw it, too.

"_I see you're angry. But I can help!" _Bill said cheerily. _"Look kid, I'm here to strike a deal."_

"I don't want any of your stupid help, Bill! I want my brother back!" she said, collapsing onto the ground next to Dipper. She turned so she could see his face. She moved some of his hair off of his face and tucked it behind his ear, then readjusted the hat he always wore - no, _had worn. _Not present tense. Not anymore.

"_Oh, but that's just why I came." _The demon came closer, and set its hand on top of Mabel's shoulder. She instantly recoiled, withering away from it.

"Get _away _from me, you creep!"

The yellow triangle floated a foot away, as though to take a defensive step back. He said, with feigned hurt in his voice, "_Come on, kid. I'm the only way you'll ever get to see your brother alive again."_

Mabel glared at Bill. "You never keep your deals. You're just a big, glowy jerk!"

Bill waved his cane around. "_What I do is called business, kid. It's something you'll understand when you grow up." _He poked her head with his cane. She cringed and rubbed the spot that'd been touched. _"So, what d'ya say? Want him up and running, or what?"_

Mabel narrowed her eyes. "Where's the catch?" she inquired, with an accusatory tone. "There's always one. What? Are you gonna make him a psycho killer or something? Are you gonna wipe his memory?"

Bill waved a hand. "_Shooting Star, I'm hurt! Do you really think I'd do those things?"_

She didn't respond, but instead glared at him.

_"I'll tell you what. All you have to do is let me jump inside him, do a little fixing, then I'll be out before ya know it!"_

"What's in it for you?" she asked warily.

Bill rolled his eye. "_Please, if I wanted him gone, he'd be dead already. Hey, no pun intended."_

Mabel didn't appear to be amused.

"_How about it?" _Bill stuck out a hand, which was enveloped in blue flames.

"Well…" Mabel felt hot, and she began to sweat. She considered accepting the demon's offer. Then she looked and saw Dipper's face, calm and peaceful. "No. I won't do it, Dipper wouldn't want me to."

_"He would do it for you. He would do anything for you."_

Mabel knew Bill was speaking the truth. Still, she frowned. Very bad things had happened last time the demon had struck a deal with one of the twins.

"Leave us alone," she said, after a moment of thought.

"_Very well, Shooting Star. Just remember, the deal can only be made for another twenty-four hours, or your brother is gone for good."_

Then the demon vanished, leaving Mabel with a sick feeling inside, and a big decision to be made.

**I hope you enjoyed reading this! Please leave a review, and let me know if it's worth continuing. I have an idea of where this story could go.**


	2. Chapter 2

**Thank you so much to everyone who read and reviewed! I'm glad you liked the first chapter. So, here's another one:**

Mabel had no idea what to do.

It was getting late, and the sun was crawling to the point in the sky where it was just beginning to dip beneath the treeline. As the bright, fiery orb that lit up the sky started its descent, so did the temperature. The girl soon found herself shivering as the forest around her quieted, the chirps of birds and scuttling of small animals growing fewer and fewer, until only a solitary bird sat somewhere up in a nearby tree, hidden by the red trees' giant branches. It produced lonely _coo _sounds, from a throat that sounded parched and sullen.

She laid there beside Dipper, her eyes on the little sky that was visible through the canopy. Mabel watched with eyes sore from crying as the gentle blue changed, morphing into an angry, hot orange, then a shocking, explosive red. The sun reached out its weakening rays, washing the trunks of the trees with a dull yellow. A dull yellow which was so very familiar…

Mabel remembered it clearly, the night she'd ignored Dipper's request for help, because she was busy trying to impress a pompous jerk. It made her feel a pang of guilt, that she had found something so trivial and stupid to be so much more important than helping her brother, who had needed her, _depended _on her. That night, Dipper had come to the puppet show she'd constructed - but he hadn't been himself.

Mabel recalled the eyes the clearest. They had been the same dull yellow that painted the trees now, as the horizon greedily swallowed the sun. She had known instantly that it wasn't the eyes of her brother she was looking into, but the eyes of a monster, and that monster's name was Bill Cipher.

Now, Mabel wrapped her arms around her torso in a desperate effort to retain her warmth. The palette of the sky was being dominated by an inky black, bedazzled with countless diamonds and a large disk that floated into the sky, chasing after the sun. She nuzzled in against her brother, until she realized he wasn't giving off any heat. This only made her eyes well up again with hot, stinging tears.

It had almost seemed like just another camping trip into the woods. Dipper had always loved to sleep outside, and stay up late enough for the moon to reveal its face. He had a fascination of the stars which Mabel never could quite understand. She used to tease him about it, and call him a nerd. Now, though, she would give anything to hear her brother go off on another long ramble about the planets and constellations. The night was devoid of noise, as though someone had flipped a switch; the only sounds that pierced through the thick blanket of silence was the faint rustling of leaves, and the distant singing of an owl.

Mabel still could save him. But at what price? Bill was notorious for twisting any sort of arrangement to fit his own sick needs. Was she really going make a deal with a demon?

Dipper was certainly worth it. Judging on his bleached-white complexion, too, it was evident that he didn't have much longer.

Mabel had to make a decision quickly, and she was afraid that Dipper wouldn't be very proud with what she was considering.

_Bill is a manipulative sadist, _she could almost hear Dipper saying, his voice being carried to her through the whispering of the leaves. _He's a bully, too, and an opportunist. He'll wait until you're in a tight spot, and then… well, I called him manipulative for a reason. _She didn't know what a lot of those words meant, but she did know that they didn't mean anything good.

Mabel glanced down at the journal. Moonlight split through the trees and reflected off of a metallic hand on its cover, which had a bold three carved into it. She had already flipped through every page in a wild attempt to find a possible cure, like a potion or spell. But there was nothing that would restore her brother to his normal self again. She'd given up and frustratedly tossed the book away.

Then, Mabel stood. She nervously glanced around at the tall trees and the long shadows they cast over her. She couldn't sit here forever, and dragging Dipper's corpse back to the Mystery Shack was not going to happen.

She had come to a conclusion. She would accept the deal, and save her brother.

"Bill!" Mabel called. She cringed - her voice sounded ugly in the nearly-pure silence of the night. It bounced shrilly off of the surrounding trees, and the rocks on the ground. It probably even reached all the way to the sparse clouds, the sound was so giant. "Bill, I accept, okay?"

A blinding blue light materialized a few feet off the ground in front of the girl. It grew brighter and larger, until Mabel found herself holding up an arm to protect her eyes. Suddenly, the blue blinked out of existence, like a giant crystal eye. Where the light once was, hovered a glowing, dull yellow triangle with arms, legs, and a single eye with an enormous black pupil which stared at Mabel until she squirmed under its pressure.

It was Bill again. Mabel was still disgusted by even laying her eyes on the demon, but this time, she found part of her grateful that the entity actually answered to her call.

_"I knew it wouldn't be long 'til I heard from you again."_

"You can really do it? You can really bring back the real Dipper?"

Bill rolled his eye. "_Of course I can. Restoring petty lives like your brother's is easy. Right now, his consciousness is still roaming around, somewhere deep in the mindscape. Basically all I gotta do is go in there, find him, and throw him back into the control room. Easy peasy."_

"Promise that you won't break the deal," Mabel said fiercely. Behind the vigor in her tone, though, she trembled with fear. Fear for her brother, and what she was getting him into.

_"Relax._ _I'll only go in, save Pine Tree, and leave. No big deal."_

Mabel thought, then nodded. It didn't sound too bad. She grabbed the hand Bill extended toward her, and shook it as both their hands were engulfed in blue flame. The demon made an approving noise.

Bill vanished, reappearing by Dipper's side. He reached out a hand toward the boy's head. To Mabel's dismay, he halted right before his fingers touched Dipper.

"But wait, there's more!" screeched Bill enthusiastically. Mabel wondered if the demon ever became tired of constantly being such a jerk. The entity laughed shrilly. "_You thought it was gonna be this easy? Haha! I'll tell you what's easy: my last sweetheart."_

"What do you want, Bill?" Mabel said.

"_Hmm, I don't know. That journal your brother sure does love a lot? That sounds like nice compensation…"_

Mabel's stomach churned anxiously. Dipper did really love the journal. He took it with him wherever he went, and it had helped the two twins solve endless mysteries.

Bill took notice to her hesitation. _ "A lousy book is a small price to pay for a life."_

Mabel frowned. "Just do it! Just save my brother, you idiot!"

If Bill had a mouth, Mabel was sure he would've smiled at that moment. The entity tipped his black hat at the young girl, then without another sound, he disappeared into the slipping mind of Dipper Pines.

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Mabel sat nearby on the ground, watching the lifeless body of her brother. It had been almost three whole minutes since Bill had disappeared, and she was beginning to grow wary.

But then, Dipper stirred. He awoke with a jolt, and the first word out of his mouth instinctively was: "Mabel?"

"Dipper!" Mabel yelled, launching herself toward her brother.

He chuckled a little as she squeezed him into a tight hug. He coughed and let out a wheeze. "Uh, Mabel...I can't breathe."

"I don't care, I'm never letting go," she said stubbornly. However, he eventually succeeded in detaching her arms from around his ribs. "I'll never lose the butterfly net again."

"Huh?" Dipper frowned. "Oh yeah, the trans-dimensional wasps!" He bit his lip as he was overcome with a sudden wave of pain. Sharply sucking in a breath, he tenderly placed his hand on his temple. "Did I hit my head or something? I have the worst headache."

Mabel wanted to explain it all to her brother that second, to burst out with everything that had just happened with Bill. Dipper was clueless; he had no idea a demon was inside his head, and this made Mabel feel guilty. She knew the right thing would be to tell Dipper, but something held her back. The only image that filled her mind was of Dipper's face, his reaction if he found out about what Mabel had done, and the deal she had made. She wouldn't be able to handle the look of disappointment he would inevitably give her.

"We should head back to the shack," she said. "Can you walk? I know! I'll carry you!"

"No, no," Dipper said, getting up on his own, though he struggled just to stand on his feet.

Mabel opened her mouth, about to say something else, but she promptly shut it. Dipper didn't need to be troubled with any details at the moment anyway; he couldn't have a worry on his mind when he needed badly to just lay down and heal. He'd be curious later, of course, but for now, the only thing that pulled at the boy's mind was the desire to lay in a warm bed.

So she decided to wait. After all, a secret isn't bad if you plan on eventually telling the other person.

Right?


End file.
